This application is based on Japanese Patent Application No. 11-280709 (1999) filed Sep. 30, 1999, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an ink jet printing apparatus, an image reading apparatus, an ink jet printing method and an image reading method.
Note the present invention may be applicable not only to a general printing apparatus but also to a copying apparatus, a facsimile apparatus with a communication system, a word processor having a printer portion, as well as an industrial printing apparatus compositely combined with various processors.
2. Description of the Related Art
Recently, the quality of a printed image output from an ink jet printing apparatus has significantly been improved to almost approach a photographic grade. As ink droplets ejected from a nozzle of a print head have increasingly been minimized in size and become dense in arrangement, a distance between the nozzle and a print medium (hereinafter referred to as a paper gap) has become more important in view of the ejection angle of the ink droplet and the stability in behavior of the ink droplet until it reaches the print medium such as paper.
There are two proposals as an automatic paper gap adjustment mechanism for maintaining the paper gap at a constant value: one being a mechanical type which detects the paper gap in a mechanical manner, and the other being an optical type which detects the paper gap in an optical manner.
According to the mechanical type automatic paper gap adjustment mechanism, however, it is necessary to bring a probe into contact with a surface of the print medium such as a paper upon detecting the paper gap, whereby there might be a risk in that the feeding accuracy of the print medium is adversely affected by the contact of the probe with the print medium. To minimize the above-mentioned adverse effect, it is necessary to prolong the probe to be an elongate arm shape for the purpose of reducing a contact resistance between the probe and the print medium based on the principle of a lever system, which results in the enlargement of the entirety of the mechanism.
On the other hand, according to the optical type automatic paper gap adjustment mechanism, the paper gap is detected even in a non-printing motion wherein no ink is ejected from the print head so that the automatic adjustment of the paper gap is carried out. Accordingly, in an ink jet printing apparatus of a serial scan type wherein the print head scans in the primary scanning direction, when the print head is shifted beyond an end of the print medium, for example, for the recovery process of the print head, a detected value output from an optical sensor movable together with the print head for detecting the paper gap suddenly changes. As a result, when the print head is out of the end of the print medium, the automatic paper gap adjustment mechanism generates an abnormal sound due to the sudden movement. There is also a problem in that an electric power is wastefully consumed because of the vacant control of the paper gap while no printing is being carried out by the print head. Also, irrespective of the operation modes of the ink jet printing apparatus, the target value of the paper gap is maintained constant. Accordingly, for example, in a serial scan type ink jet printing apparatus in which a print head and an image scanner are mounted to a carriage in a replaceable manner, a paper gap during the printing by the print head is equal to a distance between the scanner and the print medium (hereinafter also referred to as a paper gap) during the reading wherein an image printed on the paper or the like is read by the scanner. Therefore, it is difficult to establish the optimum paper gaps in correspondence to the printing mode and the reading mode, respectively. Further, since an optical sensor for detecting the paper gap is liable to be contaminated with ink mist ejected from the nozzle, there might be a risk in that the detection accuracy of the paper gap is deteriorated.
An object of the present invention is to provide an ink jet printing apparatus, an image reading apparatus, an ink jet printing method and an image reading method capable of saving electric power, suppressing noise and improving the operational reliability by specifying a timing of adjustment of the paper gap.
In the first aspect of the present invention, there is provided an ink jet printing apparatus for printing an image on a print medium by using a print head capable of ejecting ink, comprising:
detecting means for detecting a gap between the print head and the print medium,
adjusting means for adjusting the gap between the print head and the print medium based on the result obtained from the detecting means, and
limiting means for limiting the gap adjustment function of the adjusting means during the non-printing motion in which no ink is ejected from the print head in a printing mode for printing the image on the print medium.
In the second aspect of the present invention, there is provided an image reading apparatus for reading an image printed on a print medium by a scanner, comprising:
detecting means for detecting gap between the scanner and the print medium,
adjustment means for adjusting the gap between the scanner and the print medium based on the result detected by the detecting means, and
limiting means for limiting the gap adjustment function of the adjusting means during the non-reading motion in which the scanner does not read the image printed on the print medium in a reading mode for reading the image on the print medium.
In the third aspect of the present invention, there is provided an ink jet printing method for printing an image on a print medium by using a print head capable of ejecting ink, comprising the steps of:
adjusting a gap between the print head and the print medium based on the detected result of the gap between the print head and the print medium, and
limiting the gap adjustment during the non-printing motion in which no ink is ejected from the print head in a printing mode for printing the image on the print medium.
In the fourth aspect of the present invention, there is provided an image reading method for reading an image printed on a print medium by using a scanner, comprising the steps of:
adjusting a gap between the scanner and the print medium based on the detected result of the gap between the scanner and the print medium, and
limiting the gap adjustment during the non-reading motion in which the scanner does not read the image in a reading mode for reading the image on the print medium.
In the fifth aspect of the present invention, there is provided an ink jet printing apparatus for printing an image on a print medium by using a print head capable of ejecting ink, comprising:
detecting means for detecting a gap between the print head and the print medium,
adjusting means for adjusting the gap between the print head and the print medium based on the result obtained from the detecting means, and
limiting means for limiting the gap adjustment function of the adjusting means if an average printing duty of the print head per unit time is equal to a predetermined value or more in a printing mode for printing the image on the print medium.
In the sixth aspect of the present invention, there is provided an ink jet printing method for printing an image on a print medium by using a print head capable of ejecting ink, comprising the steps of:
adjusting a gap between the print head and the print medium based on the detected result of the gap between the print head and the print medium, and limiting the gap adjustment between the print head and the print medium if an average printing duty of the print head per unit time is equal to a predetermined value or more in a printing mode for printing the image on the print medium.
In the seventh aspect of the present invention, there is provided an ink jet printing apparatus for printing an image on a print medium by using a print head capable of ejecting ink, comprising:
detecting means for detecting a gap between the print head and the print medium,
adjusting means for adjusting the gap between the print head and the print medium based on the result obtained from the detecting means, and
limiting means for limiting the gap adjustment function of the adjusting means during the non-printing motion in which no ink is ejected from the print head.
In the eighth aspect of the present invention, there is provided an image reading apparatus for reading an image printed on a print medium by a scanner, comprising:
detecting means for detecting gap between the scanner and the print medium,
adjustment means for adjusting the gap between the scanner and the print medium based on the result detected by the detecting means, and
limiting means for limiting the gap adjustment function of the adjusting means during the non-reading motion in which the scanner does not read the image printed on the print medium.
In the ninth aspect of the present invention, there is provided an ink jet printing method for printing an image on a print medium by using a print head capable of ejecting ink, comprising the steps of:
adjusting a gap between the print head and the print medium based on the detected result of the gap between the print head and the print medium, and
limiting the gap adjustment during the non-printing motion in which no ink is ejected from the print head.
In the tenth aspect of the present invention, there is provided an image reading method for reading an image printed on a print medium by using a scanner, comprising the steps of:
adjusting a gap between the scanner and the print medium based on the detected result of the gap between the scanner and the print medium, and
limiting the gap adjustment during the non-reading motion in which the scanner does not read the image.
According to the above-mentioned aspects of the present invention, a function for adjusting a gap between the print head and the print medium and a gap between the scanner and the print medium is limited during the non-printing motion in which no ink is ejected from the print head in the printing mode for printing an image on the print medium and during the non-reading motion in which no image is read by the scanner in the reading mode for reading an image printed on the print medium. Thereby, it is possible to avoid an inconvenience occurring due to the excessive adjustment of the gap to save electric power, reduce noise and improve the reliability.
The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.